More than one million women are at increased risk of developing a dangerous blood clot because they are using new forms of the contraceptive pill, a study shows.

The new research from the University of Nottingham suggests that taking third generation pills such as Yasmin, Femodene and Marvelon raises the chance of a blood clot four fold compared with women who do not take an oral contraceptive.

The research was published just weeks after the death of Tamworth teaching assistant Fallan Kurek, 21, who collapsed after taking the pill, albeit an older less dangerous form.

Dr Yana Vinogradova, Research Fellow in Medical Statistics at the University of Nottingham, said that women on the newer medication should talk to their doctors about the dangers.

“Women should not stop using them, but should consult their doctor and review their current type of pill at their next appointment if there are any concerns,” he said.

“The results provide evidence for relevant authorities concerned with prescribing guidelines or those involved with regulation of safety of medicines.”

The third generation pills were launched in the 1980s and official concerns were first raised about increased DVT risks in 1995. However despite ongoing health scares, more than one third of women are still currently using the contraceptives.

They have proved popular because they are less likely to cause side-effects such as weight gain, headaches, breast tenderness and hair growth.

Blood clots which typically from in the leg can travel up the blood vessels, creating a potentially fatal blockage in the lung, known as a pulmonary embolism. They can also travel to the brain triggering a stroke.

Around 3.5 million women in Britain take some form of oral contraceptive.The team at Nottingham University used prescription data from two large UK general practice databases to measure the associations between use of combined oral contraceptives and risk of blood clots in women aged 15-49 years, adjusting for other known risk factors.

The results show that pills containing one of the newer types of progestogen hormone (drospirenone, desogestrel, gestodene, and cyproterone) were associated with an increased risk of a blood clot than pills containing older progestogens (levonorgestrel and norethisterone) such as Microgynin, the most common oral contraceptive in the UK.

Compared with women not using oral contraceptives, women using older pills, had about two and a half times increased risk of a blood clot. Women using newer pills, howereve had around four times risk.

Dr Vinogradova estimates that use of the newer third generation pills brings 14 new cases of serious blood clots each year.

However other health experts urged women not to be too alarmed by the findings.

Professor John Guillebaud, a contraception expert and author of The Pill, explains: “There is a small risk of thrombosis on the combined pill.

“The death rate of it is low but if you have got millions of people taking the pill, one or two people will have a bad outcome like this.”

Prof Guillebaud said some women should consider avoiding the pill altogether in favour of LARCS (long-acting reversible contraception such as an IUD, IUS, injection or implant)

“LARCs are so much better,” he said.

“If you had five million people on LARCs rather than the pill, there would be no thrombosis. They totally eliminate the risk. They’re also much more effective than the pill because they’re forgiving of human error. You don’t have to remember to do anything.”